Indicating mechanism



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Patented Oct. 15, 17946 INDICATING MECHANISM `Morris F. Ketay and Michael Sherman, Brooklyn, N. Y., assignors to Bendix Aviation Corporation, Teterboro, N. J., -a corporation-Lof Delaware Application September 13, 1943, Serial No. 502,210

(Cl. 'i3-388) V9 Claims.

This invention relates to indicating systems, and particularly to provision of indications of the speed and distance of travel of a maritime vessel.

An object of the invention is to improve upon the log system disclosed in 1U. S. Patent No. 1,968,539 to Rydberg, dated July31, 1934.

Another 4object of this invention is to provide means to maintain the accuracy of the mechanism in all tilted positions of the vessel, as from positions of extreme inclination to that of even keel (no roll or pitch).

vand are not designed as a denition of the limits of the invention, reference being had to the appended claims for this purpose.

lIn the drawings:

Figs. 1 and la together show the invention schematically;

Fig. 2 shows the unit master transmitter"B 'of Fig. 1, as viewed from one side with housing broken away;

Fig. 3 shows one of the rubber'shock mounts for unit B;

Fig. 4 shows the drive mechanismiorthe speed and distance indicating devices;

Fig. 5 is a fragmental sectional View showing the roller assembly of Fig. 4;

Fig. 6 is a sectional view taken along line-66 of Fig. '7;

Fig. rI is a sectional view taken along line 1-1 of Fig. 4

Fig. 8 is an end View of the roller carriage of Fig. 4;

Fig. 9 is a longitudinal sectional View of the roller carriage taken on line 9-9 of Fig. 8;

Fig. 10 shows the drive motor and geartrain for the assembly of Fig. 4;

Fig. 1l is a sectional view taken on line H-II of Fig. 10;

Fig. 12 is a front elevational view^of the main force and balance arm assembly;

Figs. 13, 14 and 17 are sectional views taken along the vrespective section `lines indicated in Fig. 12;

Figs. 15 and 16 are ragmentalplan views Aof the roller lcarrying ends of the mainforce `arm and the auxiliary balance ,arm 4shown in Fig. V12; Fig. 18 :showsa 'testing procedurelforzthe arm assemblies of Fig. 12;

Fig. 19 is a sectional View on line lil-I9 of Fig. 12, illustratingthe manner in which the scissors `links are pivotally interconected;

Fig. 20 is a bottom plan view 0f the assembly of Fig. 12;

Fig. 21 shows, on an enlarged scale, the upper part of unit B as viewed from the front;

Fig. 21A is a fragmental view on an enlarged scale `of the `switch for controlling the power motor shown in Figs. 1 and 21;

Fig. 22 shows, also on an enlarged scale, the lower .part (bellows assembly) of unit B;

Fig. 22a shows va special wrench Ato facilitate installation andremoval of the bellows rod I4;

Fig. 23 shows a `special wrench to facilitate installation and removal of thebellows cap |95;

Fig. 24 is a side elevational view ofthe assembly of Fig. -22 as it appears when viewed from the right-hand side of that gure;

Fig. 25 is a top plan view of the assembly of Fig. 22;

Fig. 26 is a fragmental side view with parts in section, of the left-hand portion of the log mechanism;

Fig. 27 is a front elevational view of the subassembly of` Fig. 26;

Fig. 28 is a longitudinal sectional view along line `213--28 of Fig. 27;

Fig. 29 shows the rodmeter assembly, including control valve;

Fig. 30 is an end View ofthe assembly of`Fig. 29 illustrating `the parts as they appear when viewedirom the right-hand side of that gure.

Fig. .31 is a view showing the opposite end;

Fig. 32 `is a view showing the handle fixture secured to the `sea rodof Fig. .29, the view being taken at righi-,angles to that view;

Fig. 33 is a sectional view taken along line 33-33of Fig. 29;

Fig. 34 is a fragmental top plan View of the end of the sea rod of Fig. 29, showing the forwardly disposed Pitot orifice in the Ysea rod;

Fig. 3.5 is a diagrammatic showing of hydraulic connections between the rodmeter and loer units;

Fig. 36 is a `diagran'irnatic view showing the stream lines about the hull of the ship;

Fig. 37 is a diagrammatic showing ofthe relationships between the Pitot -coemcient and the speed for two Vdifferent log installations;

Fig. 38 is a diagram showing-the elect of the A adjustment upon-the Pitot coefficient;

Figs. 39 -and 40 are diagrams showing various relationships between L.the measured distance and the log indicated distance; and

Fig. 41 is a diagram showing the eiect of the B adjustment upon the Pitot coeicient.

In Figs. 1 and la the complete system is shown schematically as including a rodmeter A, a master transmitter-indicator B, and receiver indicators C, D and E. The master transmitterindicator B isv mounted above the ships bottom 2, but below the ships waterline (see Fig. 35), and consists of a series of electro-mechanical linkages and a bellows assembly 5, I I, I3 which is divided into two chambers by means of diaphragm I2. A rod I4 moves with the diaphragm I2, to which it is attached.

The upper part of the bellows chamber is connected with the sea (indicated at I, Fig. 1) through the static line I containing control valve 3SI, and through static openings 4, one on each side and one ush with the bottom of rodmeter A, the latter extending through the ships bottom, indicated at 2 in Figs. 1 and 35.

rThe outer part of the bellows chamber is connected with thesea through the Pitot or dynamic line 6 containing control valve 382, and the Pitot orice 3 of rodmeter A. Due to equalization of static pressures acting thereon, through lines 6 and "I, diaphragm I2 will remain stationary when the ship is at rest.

With the ship in forward motion (or for an increase in speed), an extra pressure ("speed pressure) is created in the Pitot orice 3, causing vdiaphragm I2 to rise due to unequal Pitotstatic pressures. This movement is transmitted to the scissors mechanism by means of rod I4, and the scissors mechanism (see Figs. 12 and 14) causes the main balance arm I3 to pivot clockwise about its pivot shaft 95 (see Fig. 17), thereby causing electrical contact 26 to close a circuit to energize actuator motor 45, the motor energizing circuit being in several branches, including the wires shown in Figures 1 and 21A as proceeding from contact segments 2I-254 engageable by the contact element 20. Energization of these wires leading to the several windings of motor 55 produces rotation of said motor, which rotates cam 25 clockwise (through mechanical connections 4E, lil, I5, 42 and 22S-Figs. 4 and 10). As this movement proceeds, it causes main force arm 23 to pivot in a counter-clockwise direction to stretch main spring 23, causing main balance arm I S and Contact 22 to return toward their neutral position, thus eventually cutting ol current flow to motor 45, when the neutral position is attained. Rod ld and the attached bellows are accordingly depressed by the cam action into their original positions and a certain amount of water is forced back into line 6. Main force arm 23 however, remains in its new (spring tensioning) position, and pointer 21, attached to the shaft 22S of cam 25, whose angular position reflects the angular position of arm 23, except for the fact that the cam is given a contour to convert the non-rectilinear relationship between bellows pressure and speed into a straight line relationship on the indicator dial whereby the latter may be provided with scale divisions of equal value, will then indicate the ships speed on scale 25.

Upon a decrease in speed, the rod I4 moves downward, allowing main balance arm I8 to pivot in a counterclockwise direction. Contact 20 then closes another circuit and starts the actuator motor 45 in the opposite direction, turning cam 25 counterclockwise, which causes main force arm 23 to pivot clockwise, reducing the force transmitted through spring 28, until main and the speed is expressed by the following formula:

P=K1J2 where P is the pressure, K a coeicient (hereinafter called the Pitot coefiicient) and v the speed of the ship.

If the Pitot opening should move in absolutely undisturbed Water, the Pitot coelicient K would have a value equal to 1. Actually, the water surrounding the hull of a moving ship is disturbed. The stream lines will diverge and converge, as shown on Fig. 36, the angles varying with the speed of the ship. Also, the depth of the layer of water that is dragged along with the ship Varies at different places of the hull and varies with the speed of the ship. The degree of disturbance varies in an inverse ratio with the distance from the hull, until it is at a certain distance nil. This latter distance, in turn, varies with the speed of the ship. Therefore, the degree of disturbance at the point of the Pitot opening will vary with the diierent speeds of the ship (unless the Pitot tube were to be made long enough to extend beyond the region of disturbance, but this is for practical reasons very seldom possible).

The Pitot coeicient K in the above mentioned formula therefore represents the reducing or corvrecting inuence to compensate for the eiect of this variable disturbance factor on the speed pressure.

Experience has proven that the value of this coefficient K (plotted against speed) may be represented as a straight line, for example, A or B (see Fig. 37). Of these, the line A represents the 'more common condition encountered in practice.

. To make it easier` to understand the calculations for the proper adjustment of the log, the error of the log will, in the following, be expressed as so many per cent (-lor of the true speed, instead of in the form of Pitot coefficient. Comparing the two ways of expressing the error of the log, it will be found that if the Pitot coeicient to which the log is adjusted is too low compared with the actual Pitot coeicient of the ship, the log will indicate too high a speed and a greater distance than that actually travelled, giving a positive percentage error. If, on the other hand, the log is adjusted for a Pitot coefficient that is too high, then the percent of error will be negative.

Without adjusting means, the error of the apparatus would, with a Variable Pitot coefficient, also be variable. This variation may gradually increasefrom say 2% at low speeds to 6% at high speeds, or decrease from say 6% at low speeds to 2% at high speeds.

The disclosed apparatus has three adjustments, designated herein as A, B and 0.

The C adjustment (internally threaded sleeve I6, Figs. 1, 12 and 14) relates only to the adjustment of the zero position of the mechanism, i. e. to bring pointer 2'I to zero when the ship is at rest.

The adjustment A is for the adjustment of the main spring 28 (Fig. 1) through increasing or decreasing the number ofeffective windings of the same. The adjustment B is for Ithe adjustment of the regulating effect of the auxiliary spring 2l (Fig. l) on the moment `exerted by auxiliary arm I9 upon'themain lever It.

By means of adjustments A 4and "B Vthe apparatus isset for the actual Pitot coeiiicientof the ship, as determined by runningthe shipove'r a measured course. Y

Figures 38 and 41 illustrate the inuence-ofthe adjustments A and"B upon the mechanism, from which it is observed that the effect of .the A adjustment is constant at all speeds, whereas the B adjustment maybe so carried out as .to

manifest either an increasing or decreasing action as the speed increases.

Fig. v3'? is a graph showingl the relationship between-the Pitot coefcient and speed for two different installations from which it is observed that astraight line ratio exists in both instances. In most instances however, the relationshipwill assume the form of line A, with the coeflicient increasing with the speed. 1

VIn Fig. 39 the relationships between .the measured mile `and the mile as indicated by the log are illustrated, theleft-hand diagram showing a negative error, with the indicated mile shorter than the actual distance, the middle diagram showing the correct setting with Vthe indicated and measured distances equal, and the righthand diagram showing'a positive error.' Fig. 40 diagrammatically shows the results `of several readings taken over a comparatively longmeasured run.

At first, the B adjustment issupposed to be set in its zero position. When thespeed-indicating hand leaves zero, the sector 32 (Fig. 1) moves downward and continues to descend until the prevailing speed is reached. With the 13" adjustment in the zero position, this movement will not have any influence on the roller attached to the arm 3l of the auxiliary lever AI 9 (Fig. `1) the roller remaining in the same position during the whole time, as will behereinafter pointed out. Therefore, the system will not be influenced by the auxiliary tension spring 2l, but only by the main tension spring 28, and equilibrium will be obtained when the latter spring is moved into a position for which its moment, (tension a times leverage b) is equal to .the moment of the force of the bellows (c times d) on the same lever.

The tension of the main spring, however, can be adjusted by screwing plug 29 (Fig. 1) into or out of the spring, thereby varying the number of eiective turns. This is adjustment A. By decreasing or increasing the number of effective turns, the spring will be made stiffer or weaker. Thus if the system (when tested by running the vessel over a measured course) should indicate too high, the main spring 28 must be stiffened (A adjustment increased in numerical value) so that the moment is increased to obtain correct indications. The effect of such an adjustment is graphically illustrated in Fig. 38. The line A represents a certain Pitot coefficient and the lines Ai and An represent, respectively, the new values of Pitot coefficient when the number of effective turns of the main spring is decreased orV increased, it being observed that the `effects of the several adjustments remain constant forall speeds.

Now, if the adjustment B (screw 33, Fig. 1) is set to the right of its zero position, the sector 32, when moving downward will force the auxiliary lever 3H (through its roller) to the right. The auxiliaryspring 2l will then be pulled to the right and atthe 'same time stretched, whereby it vwill -eXert a moment Aon `the -main 1lever acting op- `positelytolthe moment of themain spring 28and thereby reducingA the eiect of the same `on` the 'mainleven t p Likewise, if the adjustment B is set to thele'ft, the runner -32 will force the auxiliary lever 3| to `the left, whereby the moment of Athe auxiliary spring on the main lever will addto the moment Jof the main spring on that lever.

`When the speed indicating hand 21 points to zero, the-setting of the B adjustment on either side of its Zero position d-oes not have any effect on the roller, between the guides of the runner, because the axisof the roller then coincides with the axis of sector 32, but as soon as the hand leaves its Zero position, the increasing or decreasing effect of the auxiliary spring will increase with the speed, and the further to the left `or to the right'the B adjustment is set, the greater will this effect be. Fig. 41 shows graphically the influence of the B adjustment on the Pitot coefficient. The line B represents the Pitot co- `efficient with the B adjustment set at zero. B1 shows the effect of the B adjustment set to the left. Bn shows the effect of the B adjustment set still further to the left. Bm shows the effect of the B adjustment set to the right, and BIV shows the effect of the B adjustment set still further to the right. It is thus obvious that if the Ptot coefficient is increasingwith the speed, the B adjustment Vmust be set to the left in order to increase the moment on the main lever to balance the increased moment of the force from the bellows on that lever, and bring about'correct indications.

If, on the other hand, the Pitot coefficient is decreasing with increasing speed, the B adjustment must be set to the right in order to decrease the moment of the springs on the main lever and balance the decreased moment of the force from the bellows.

`From what is stated above, it will be understood that by meansof the A adjustment, a correction can be performed which affects all indications alike with a constant percentage as the speed increases, and by the B adjustment there is effected a correction which aifects the indications with an increasing or decreasing percentage as the vessels speed increases.

Motor 45, which drives the cam 25 through shaft 4l, also drives gears 35, screw 36, gears 3T and screw 3B, positioning carriage 61 and friction wheel 39 along the surface of disc 40, the latter being driven at constant speed by a synchronous motor lll a worm 48 and a worm gear E. The driving ratio of friction wheels mand 39 thus varies directly as the distance from the point of frictional Contact to the center of disc 4S; and since the follower 39 is driven by the sanremo-tor 45 that positions the speed pointer 21, it follows that the distance from the frictional `contact point to the disc center varies directly as the ships speed. 'When follower 39 is therefore set sn that when the log indicates Zero speed, it is at the center of disc 40. Therefore, the mileage odometer 'l2 (shown in Fig. la as electrically and mechanically coupled to the follower 39 through differential'24 and synchronous units 55 and l0) will indicate the distance travelled (nautical miles).

The unit C (Fig. la) includes not only the odometer 12 but also a speed dial I0 and pointer 68, operated b-y a self-synchronous motor 67 connected to a synchronous unit 48, the latter being shown in Fig. 1 as driven by gears 5| and 52, which are in turn driven by power motor 45 "throughconnections 4B, 41, I 5, -42 and 220ewhich 7 drive speed pointer 21 (see Figs. 4 and 26). The arrowheads in the lower portion of Figure 1a denote connections to sources of alternating current.

The units D and E (Fig. 1) are electrically synchronized with synchronous generators 43 and 55, respectively.

Rotation proportional to the speed of the ship is transmitted to pointer shaft 220 (Fig. 26) by gear 42, which is fastened to that shaft and driven by a worm I on shaft 41 (Figs. 1 and 4). The latter is driven by power motor 45, through a pinion I4I on the motor shaft meshing with a gear 46 on a worm-shaft 30; a worm |44 meshing with a worm gear |46 carried by a shaft 44; and a gear |41 on shaft 44 which meshes with gear |49 on shaft 41. The cam 25, fastened to the pointer shaft 229 is so designed that in turning an amount proportional to the ships speed, it restores to neutral the main force and balance arm assembly 23-I8-I9, thus moving contact arm 20 to neutral position and shutting off the power motor 45. This speed indicating rotation is transmitted by gear 5I (on the pointer .shaft 220) to gear 52, in such a ratio that 240 rotation of the pointer shaft 220 results in 360 rotation of the gear 52, and hence of the synchronous generator 48, which is driven by said gear (Fig. 26).

The novel means for amplifying the torque available for operating the distance transmitter 55 is best shown in Figs. 26, 27 and 28, and includes a differential 24 and a follow-up motor 62, each geared to transmitter 55. Motor 62 is connected to motor 55 by means of a pinion 63, a gear 64, a pinion 65, and gear 66 fixed to the shaft of motor 55. A bevel gear 235 on the shaft of transmitter 55 meshes with a gear 223 carried by a sleeve 6I journalled in one arm of a pedestal 80. Rotation proportional to distance travelled is transmitted from disc 39 to the differential 24 through the universal joint 42. With the transverse spindle of differential 24 stationary, the two differential gears 53, 54 transmit (with a reversal of direction) the rotation of input gear -56 to output gear 51. Through bevel gears 223 and 235 (Fig. 28), and a hollow shaft 6I, output gear 51 drives the distance transmitter (synchronous generator) 55.

A rheostat 60 controls the torque output of motor 62, and is operated by a shaft 233 extending from the spider of differential 24, which carries the gears 53 and 54. When the reaction of the load on the distance transmitter 55 exceeds the friction of rheostat 69, the output gear 51 of the differential revolves more slowly than the input gear 56, and the spider of the differential rotates, turning shaft 238 and rheostat S0 in such a direction as to decrease the resistance, causing the follow-up motor 62 to supply additional torque to the unit 55. Similarly, when the output gear 51 revolves faster than the input gear 56, the differential shaft 23S turns rheostat 60 in such direction as to increase its resistance, causing a decrease in the torque supplied to the unit 55 by follow-up motor 62. Thus, the differential 24, in combination with motor 92, functions as a power amplifier and keeps the input and output gears revolving at synchronous speeds without overloading the integrating mechanism.

Should the arm of rheostat 60 reach the limit of its motion before synchronism is attained, additional load is applied to the integrating mechanism, but before slipping can occur between the disc 40 and follower 39, the rheostat arm slips on its driving shaft. Any suitable type of fricsecure the rheostat arm to its shaft. Rheostat 60 is of such electrical value that when it has reached the maximum resistance position just referred-to, induction motor 62 still supplies a small torque to the transmitter 55. It will reach that position, however, only at low speeds and small loads, and under these conditions the speed of the output shaft 8| is held to the speed of the input shaft 42 by the friction between driving disc 40 and follower 39. At high speeds and large loads, however, the torque output of the induction motor 62 is adjusted to the load through the above-described novel control of rheostat 60.

As heretofore noted, the main force and balance arm assembly (Figs. l2 to 2l) consists of three levers: the main balance arm I8, the main force arm 23, and the auxiliary Ibalance arm I9, which together form the equilibrating arrangement. The main balance arm has a counterweight 94, which brings its center of gravity into the center line of balance shaft 95 (Fig. 17) about which it pivots on ball bearings 96. Counterweight 94 is not intended to be moved from its position, as this would cause errors in readings, uncorrectable by the adjustments provided. Similarly, main force arm 23 carries a counterweight for balancing it.

The moments acting on the main balance arm I8, which maintain it in equilibrium, are produced by:

1. The force produced by the bellows and transmitted through the rod I4 to the main balance arm I8 (see Fig. 12)

2. The force produced by the main spring 28 acting through an anchor screw |02 on the rocker bearing 98, attached to the upper end of the main balance arm I8 (see Fig. 17); and

3. The force produced by the auxiliary spring 2| acting on spring holder 99 and anchor screw |00 attached to the upper right portion of the main balance arm (Figs. l2 and 13).

The top of the rod I4, as shown in Fig. 14, has a cap |0I receiving a pin 299 to which are pivotally attached the arms 300 of the scissors arrangement, which scissors arrangement also includes arms 30| disposed on either side of the pivot member 91 (Fig. 14), which in turn is slidably received in the bracket 25| extending. laterally from the main arm I8. The corresponding arms 300 and 30| of the scissors are pivotally connected to each other within the depending leg 241 of the bracket 25|. A tension spring I1 acts upon the ends of the scissors elements, and the joint thus formed is adapted to exert a constant pressure urging fulcrum |05 of cap IOI into into engagement with its seat in bearing member 91. The latter and fulcrum |05 convert vertical movement of the rod I4 (in either direction) into a swinging movement of the main balance arm I8 about its pivot shaft 95 (see Fig. 17). For each turn of the micrometer thimble I5, the micrometer barrel |03 moves upward against micrometer spring |04 a distance of 0.1 inch, which is transmitted to the main lever at the pivot 91, thereby providing a zero adjustment, called the C adjustment. The number of turns, as well as fractions of turns, can be observed on the scale provided, and the whole arrangement locked by means of a stop screw threaded into a boss |96 (Fig. 12). The stop screw is threaded into sleeve |03 and bears against the shank of screw I4' so as to lock the two parts against relative rotation. The C adjustment changes the effective length of: the rod I4 connectingthe bellows-,to the mainv under the action of thev main cam upon ball bear` ing roller 42 (Fig. 12), which is kept in contact with the cam by a force load spring 28.

The adjustment ofthe main spring 28 is effecti ed by turningy the spring thirnble 29 fastened to the spring adjustment screw Ill, whereby the number of effective windings of the spring is increased or decreased. Thel number of turns can be read off on the thimble scale (Fig. l2) and' fractionsof turns on the rim of the thirnble itself. This is called the A adjustment, and af fects' the log indications by the same percentage at' all` speeds. Referring to Figs. 12 and 1.4, a dependingbracket 241 carried by a side arm 25| formed on lever i8 cooperates inv guiding relationsliip` with the sides of scissors elements 350 and 3|l|1 to prevent bodily rotation of theV latter ab outta .vertical axis;

The upper end of the auxiliary spring` 2| is attached; tothe top of the auxiliarybalance arm la: (Fig;.13 by means of spring force hub |22 mountedzinball bearings |23. The auxiliary balance arm I9: is` forlnshaped so as to straddle balance arm If and pivots on' ball bearings 95 (Fig. 17) about balance shaft 95', the latter being journalled in the frame inl bearings |01. An arm. 3f carriedby the upper end` of the auxiliary balance arm isiprovided at its outer end with two ball bearings |25A that ride between two guides carried'. by sector 32:, which by means of the B` adjustment are madel to rotate the auxiliary balance arml through an angle proportional to the` speed of the ship, introducing an auxiliary moment, whichy affects the readings by a con-` starrt. rate of increase or decrease of percentage as the speed` increases. This B adjustment is effected' by rotation. of knob 33.

Rotation of knob 33, by hand, turns a worm H4 which rotates gear sector 32 and roller guide i513 about pivot |55, changing the anglethe roller guide makes with the lead screw 35, a measure of which is indicated on B scale 34 by pointer tl (Fig. fl). As seen in Figs. 4, 6, and 7, guide |58 has a high side and a low side for coacting engagement with the two rollers |25., without` lost motion. Sector 52 is carried by a slide IIB which is guidedfor movement on a pair of bars or rods |55. The latter are so located that a radius from shaft B5 will bisect guidesv |55, when neutral position. Therefore when the guide is in its neutral position, movement of the slide will not produce movement of auxiliary arm I9.

If? the roller guide is rotated-clockwise from thev zero position (guide parallel to lead screw), the auxiliary balance arm is rotated clockwise, introducing a moment opposing that of the main forcev arm, causing the log to indicate for aV constant` speedv pressure av higher speed than that obtained with the roller guide parallel to the lead screw. Similarly, counterclockwise rotation of the roller guide from its Zero position produces for aconstant speed pressure a lower speed indication than that obtained with` the roller guide parallel to. the lead screw. This B adjustment, as noted, affects the log indications by a constant rate of increase or decrease in percentage as the speed increases.

It should. be particularly observed that at zero speed the axis of rollers |26 coincideswith the axis of segment 32. Accordingly, the latter may be adjusted at zero speed without increasing or decreasing the stress in either the main or auxiliary tension springs. Leadscrew :a engages a nut |54 on the slide and propels the latter along its guides.

Contact arm. 2i) holding. slide contact |32 is fastenedtothe main balance arm through the contact pivotV |34 and the contact arm support 5.36. the-.contact surfaces at all times. The action of the contacts and the power motor are described hereinafter.

Spur gearV titl (Fig. lo) on the shaft of power motor. 55 meshes with gear 45, turning wormv |44.

carried by a shaft 371i. As shown in Fig. 11., worm wheel` |45 isy on a shaft 44 which also carries av spur gear |41, the latter meshing with a gear |49, which, as shown in Fig. 4, is mounted upon and operates the worm shaft 4T.. Worm shaft 41 drives worm I5, which in turn drives worm wheel 42, the latter being keyed to shaft 220, as is also the cam 25, as shown best on. Fig. 26. Bevel gear 35 on the drive shaft ill drives another bevel gear which turns lead screw 35, meshing with follower nut. |54 (Fig. 6). When the speed of the ship increases, this follower nut, together with. gear sector and roller guide |56, is driven downwardly along slide shafts `|58 (Fig.` 7). Since thevslidel llt and cam 25 are permanently interconnected by shaft 4l and the associated gearing, it is apparent that for any given angular position of cam 25 theslide IIS` will assume a predetermined position along its guides.

Thus the movement of roller guide |55 is proportional to speed variation, and causes the BP correctionto be automatically effective upon the actionof contact arm 2|), so as to out off current flow to motor. 45 at the proper point in the movement of. speedV pointer 21.

At, the upper end of the lead screw shaft` 35 isa bevel. gear drive 3.1 which turns center lead screw 38', journalled inframe It?. (Fig. 8). The latter slidably supports a guide rod. I'IIJ which in turn-supportsfa pair of arms |24 and |25. As seen in Fig. 9, armv |24 has a nut portion |21 meshing with lead screw 38. Arm |25 is forked, so'as to straddlefarm |24 and. roller 39 is journalled in the two legsthereof as seen in Fig. 5. Thelegsare alsolprovided with adjustable stop screws |23 whichv cooperate with limit switches |81,` |82, and. |83. A spring I'II acts upon portions of arms |24V and |25 so as to constantly urge the roller toward the disc.

To sum up, the following devices are driven by. the power motor `45: the main shaft 41 and cam 25 and pointer shaft 222, the screw spindle ofl the runner of the B adjustment, and thescrew spindle 33 of the distance transmitter which moves the friction wheel 39 across the face of the constant speed disc 45.

Follower roller 35` (Fig. 5) is pinned to the universal joint 42 which rotates on ball bearings mounted. in the legs of forked arm |25. Spring |.ll` (Fig. 8) keeps the proper pressure between follower roller` 39 and driving disc 4E). Joint 42 provides sufficient endwise lost motion or play to permit roller 39 to move from the center to the periphery. of disc (l. The` disc is driven at constantspeed. by. synchronous motor 4|, through aw-orm S anda worm gear 9which provide the desired speed of rotation of disc 40 as heretofore pointed out. (Fig. 1). Motor` 4| isrconnected to Spring 6.3.1 vkeeps the proper` pressure atl 

